<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="UTF-8" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
    <title>Document</title>
  </head>
  <body>
    <script>
      const jack = { name: "jack", age: 20 };
      const lili = { name: "lili", age: 20 };
      const lucy = { name: "lucy", age: 20 };
      let wset = new WeakSet();

      wset.add(jack).add(lili).add(lucy);
      wset.delete(lili);
      console.log(wset.has(lili));
    </script>
  </body>
</html>
